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New laser gas system saves $47,000 annually: with the design and installation of a $22,000 gas system for its welding and cutting lasers, an automotive supplier is on the road to saving an estimated $47,502 every year in gas, cylinder, and maintenance costs.

Flex-N-Gate Forming Technologies (Warren, MI) uses laser cutting and welding machines to produce a wide range of automotive products including bumper systems and injection molded consoles for the Chrysler PT Cruiser, Dodge Ram, Chevrolet Silverado, and Ford Explorer, to name a few.

The laser department operates three NTC 5-axis laser centers that utilize carbon dioxide lasers operating with carbon dioxide, helium, and nitrogen gases to trim out metal stampings. The three gasses used in the laser systems are extremely sensitive to atmospheric contamination. Among the most serious contaminants are hydrocarbons. Deposited on system components, such as mirrors and lenses, hydrocarbons result in a condition referred to as optic absorption, which causes distortion of the laser beam, reducing the laser's production power.

[ILLUSTRATION OMITTED]

"We were experiencing heavy maintenance issues," says Tony Podsiadlik, department supervisor, Flex-N-Gate. "Whatever (gas) you put inside the resonator must start out pure and then be delivered without introducing contamination. Otherwise, the beam quality will deteriorate."

The accompanying Figures graphically illustrate how this contamination deteriorates beam quality. As the beam spot size increases, the power density (W/c[m.sup.2]) of the beam is reduced. Figure 1 illustrates a top view of an ideal laser beam surface area that has been burnt into an acrylic block during a simple mode diagnostic check. It is evident that Figure 2 will have a lower power density due to the wider dispersion and splitting of the beam. This reduces cut speed and quality.

[FIGURE OMITTED]

$2,700 Maintenance

"We were performing frequent maintenance every three to five weeks, which was creating heavy expense and downtime," says Podsiadlik, adding that each machine required 10 hours of maintenance to complete (at $120/hour) and $1,500 in parts.

Flex-N-Gate's gas supplier, Airgas, identified the maintenance problems as systemic and began to design a gas delivery system to counter the maintenance expenses.

"The goal was to improve the laser gas delivery system--the right way, with continuity of service and purity as primary objectives," says Jim Pangborn, Airgas, "Since lasers use gases in several ways, we needed to evaluate the assist gas situation, resonator gases used to generate the laser beam, and the beam purge gas."

Flex-N-Gate was using individual gas cylinders to feed its laser system. Taking the systems approach to the Flex-N-Gate problems. Pangborn brought in Bob Montgomery, an engineer from Concoa (Virginia Beach, VA), a gas equipment manufacturer.

Montgomery's recommendation incorporated automatic cylinder changeover systems to eliminate downtime and the frequent need to change cylinders.

[ILLUSTRATION OMITTED]

The CONCOA installation Montgomery recommended includes three different automatic changeovers for constant flow of high-purity gases needed for the resonator. If one side of the system empties, an alarm goes off and automatically switches to the other cylinder--and laser performance is uninterrupted. The older method utilized a single cylinder that allowed atmospheric contamination when exchanging cylinders. The new system utilizes stainless steel tubing and hoses with built-in check valves at the inlet to keep atmospheric contamination out and maintain purity even during cylinder changeouts.

Continuous & Pure

Continuous and pure are key factors, he emphasizes.

For the assist or process gas, which is used at the laser head to aid cutting, the new installation includes an outside bulk cryogenic oxygen vessel to replace individual cryogenic liquid oxygen dewars that were used and stored inside. This solution eliminates the need to change cylinders (the bulk vessel is refilled periodically by an Airgas cryogenic transport), reduces product cost, and eliminates the possibility of running out of gas.

The system CONCOA and Airgas designed consists of manifolds, switchovers, alarms instead of individual cylinders without alarm capability for the resonator gases, and outside bulk cryogenic oxygen storage for the assist or process gas. This system eliminates the need for many individual pieces of equipment, provides for a safer work environment, and reduces costs.

"Now there is continuous gas flow," says Montgomery. "The goal of the new system is to protect the integrity of the gas supply. Its centralized location, manifolds, and alarms assure just that."

Also, stainless tubing and compression fittings eliminate permeation of atmospheric contamination in the delivery lines. A Model 624 laser gas distribution panel at each unit enables operators to observe pressures on the spot and adjust them as necessary.

The gas distribution system also includes two-micron filter assemblies at the final point of filtration prior to the gases' entering the laser. Montgomery recommended the Model 623 Series regulator for the assist gas because it has a quick response time from static flow, and works well at low-inlet pressures--exactly what is needed to ensure laser performance.

Pay-Back

To facilitate economic analysis, Podsiadlik supplied Pangborn with laser maintenance records and repair costs for the previous year.

The new gas delivery system, which cost $22,000, would require no maintenance for a one-year period--allowing for production of 1,300 pieces--as opposed to the previous system's three-month maintenance cycle and production of only 300 pieces.

Total projected savings for the laser and assist gas systems, Pangborn concluded, amounts to $47,502 per year. This number includes:

* $16,764--the cost of laser maintenance and parts for two years, and downtime;

* $15,555--the projected productivity savings on the cost of cylinder rentals and changeouts, and

* $15,183--the annual savings on assist gases.

The payoff on the initial $22,000 purchase, Pangborn determined, would be achieved in eight months. Initial projections validate the payback period.

For Podsiadlik, the Airgas/Concoa installation has provided his laser department with many added benefits that range from improved performance, smooth and efficient operation, to less maintenance, and cost savings on gases.

"We're using 50% less gas than before," he says. "We do a lot of aluminum. The increase from 300 pieces to 1,300 pieces before needing maintenance is quite impressive." Concoa

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Title Annotation:Lasers
Publication:Modern Applications News
Date:Mar 1, 2004
Words:967
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